Manufacture of netting

ABSTRACT

The invention provides an improved apparatus for producing recilinear mesh netting from threads containing thermoplastic material. In manufacturing netting in accordance with the invention transverse threads are drawn across parallel longitudinal threads and discrete masses of thermoplastic material in heated condition are moulded in respective dies about the thread crossings. The path of each transverse thread between the dies is extended by an amount corresponding to the contraction of the transverse thread which occurs in the moulding operation. The apparatus is preferably fitted with adjustable thread diverter elements between each die so that the extent to which the transverse thread deviates can be varied to correspond with the shrinkage incurred in each particular case, depending on the nature of the threads employed and on the number of longitudinal threads or the mesh size. Netting produced in accordance with the invention can be used for a variety of purposes for example in sports or for fishing and when electrically conductive threads are employed the netting can be used for electrified agricultural fencing.

United States Patent [191 Bramley 1 Jan. 30, 1973 154] MANUFACTURE OFNETTING [76] Inventor: Anthony Bramley, Gosford House,

[52] U.S. Cl ..42S/l09, 140/10 [51] Int. Cl. ..B28b 19/00 [58] Field 01Search ..l8/30 PP, 30 PM, 30 PT,

30UM; 140/10,11, 12, 13, 14, 15;42s/109 The invention provides animproved apparatus for producing recilinear mesh netting from threadscontaining thermoplastic material. In manufacturing netting inaccordance with the invention transverse threads are drawn acrossparallel longitudinal threads and discrete masses of thermoplasticmaterial in heated condition are moulded in respective dies about thethread crossings. The path of each transverse thread between the dies isextended by an amount corresponding to the contraction of the transversethread which occurs in the moulding operation. The apparatus ispreferably fitted with adjustable thread diverter elements between eachdie so that the extent [56] References Ci d to which the transversethread deviates can be varied to correspond with the shrinkage incurredin each par- UNITED STATES PATENTS tlcular case, depending on the natureof the threads 3,340,570 9/1967 Korf ..l8/30 UM X p y and the number Oflongitudinal threads 1,075,374 l0/l9l3 Parrish ..I40/l5 X or the meshsize. Netting produced in accordance with 3,084,720 4/1963 Yaeger ..l40/l0 X the invention can be used far a variety f urposes for example insports or for fishing and when electrically Primary Examiner-KllbyJrconductive threads are employed the netting can be Blanchard andFlynn used for electrified agricultural fencing.

[57] ABSTRACT 9 Claims, 4 Drawing Figures J J l i l MANUFACTURE OFNETTING The present invention relates to the manufacture of netting.

In US. Pat. No. 3,501,366 there is described and claimed netting whichis composed of regularly and preferably rectilinearly arranged flexiblethreads which consist of or contain thermoplastic filaments, the threadsbeing joined to one another to form netting by masses of plasticsmaterial individually moulded and bonded to each thread at each threadjunction. The netting can be made by drawing transverse threadscomprising thermoplastic material across longitudinal threads alsocomprising thermoplastic material and moulding discrete masses ofthermoplastic material in a heated condition about the threads atcrossing points.

Such netting can be manufactured in apparatus which includes means foradvancing a plurality of Iongitudinal threads, means for drawing atleast one transverse thread across the longitudinal threads, a pluralityof operable die assemblies each adapted to receive and enclose portionsof one longitudinal and one transverse thread at a thread crossing, andmeans for introducing heated plastics material into the die assembliesto form a moulded mass therein. The die assemblies may be provided in amultiple moulding head extending across the width of the net-makingmachine, and may be openable simultaneously between moulding operationsto permit intermittent advance of the netting being produced.

It has been found in the practical operation of this method of producingnetting that the hot moulding of the plastics masses leads to acontraction of transverse thermoplastic threads of the order of 0.010inch per moulded mass. In the manufacture of coarse mesh netting, forexample for fencing purposes, this contraction is of little account, butwhere a relatively large number of thread junctions occur across thewidth of the netting, as in the case of sports or fish netting, theshrinkage which occurs can give rise to difficulties. Not only is thewidth of the netting produced less than that expected from thedimensions of the moulding head, but problems arise from the deviationof the longitudinal threads which occurs as they pass the line of dies.The problem is particularly acute where moulding heads are employedwhich apply two or more rows of moulded masses simultaneously.

Attempts to offset the shrinkage in the transverse direction by spacingthe dies more widely than the desired spacing of the thread junctions,by the amount necessary to compensate for the shrinkage, have notprovided a satisfactory solution to the problem because they do notavoid the difficulty of non-rectilinear advance of the longitudinalthreads through the moulding dies.

-It has now been found that this problem can be solved by providingthread diverting means arranged to extend the path of a transversethread between the two adjacent dies to an extent corresponding to thecontraction occurring between the die centers. In the preferredapparatus, thread diverting elements are provided for this purposebetween each individual die in operation.

The diverting elements may be fixed and may, for example, be in the formof convex surface provided on the structure between the dies acrosswhich the transverse thread passes, but it is preferable that theyshould be adjustable, so that allowance can be made for differentproperties of different types of thread that may be used. Moreover, the'use of adjustable elements makes it possible to employ the principle ofthe present invention in universal net-making machines, in which thenumber of dies actually in use at a given time, and hence their spacing,can be varied by selectively shutting off those dies not required forthe type of netting to be made. In such a case, the diverting ele' mentscan be selectively adjusted to ensure that the correct compensation forshrinkage occurs between each die in use. Adjustable elements may bemounted on screw threads and have heads formed with several intersectingguide grooves. Depending on the number of intersecting guide grooves inthe head of the element, the increment of adjustment will be thecorresponding fraction of the pitch of the thread on which the elementis mounted.

The diverting element should have a surface which provides a smooth pathfor the thread, for example a convexly arcuate path. It is preferredthat the element should be provided with a groove or guideway to guidethe transverse thread and to maintain it in the path which ensures thedesired length of deviation. Guides may also be provided in or adjacentto the dies to ensure that not only the transverse but also thelongitudinal threads are accurately located within the dies for themoulding operation.

The apparatus of this invention is useful for making all types ofnetting from threads or twines containing thermoplastic material. Thetwines may be wholly of plastics material, as for example in the case ofsports or fish netting, or may include metal filaments as in the case ofnetting for electrified fences. With a given machine having a standardspacing of dies across the width of the machine, the mesh size can bevaried in multiples of the standard spacing by varying the number oflongitudinal threads employed, the unwanted dies or injectors beingdisconnected. In such a case the diverter elements will not allnecessarily be adjusted to an identical vertical position but areadjusted to compensate for the shrinkage actually incurred in each mesh.

In accordance with another aspect of this invention it has been foundthat a more regular result is achieved if the transverse threads, onbeing drawn through the open dies and cut, are only loosely held attheir opposite ends as the dies close so that the ends can be drawn inas the threads are enclosed in the dies and local or unequal tension onthe threads is avoided.

This feature is of general application in machines for making netting bythe application of moulded masses to thread crossings, but is ofparticular value when thread diverting elements are also employedbecause the diversion or displacement of the transverse threads betweenadjacent dies would give rise to more serious tension problems in theabsence of this further feature.

In the apparatus of this invention, the loose control of the ends of thetransverse threads can be provided for by upper and lower gripperelements respectively associated with upper and lower die portions anddisposed in pairs at the ends of the row of die assemblies, the gripperelements being arranged to close' as the dies move to the closedposition and to reach and remain in a position where they loosely grip atransverse thread before the dies are completely closed. The uppergripper elements may be fixed to or with respect to the upper dieportion structure and the lower gripper elements movable with butindependently of the lower die portions.

In a particularly advantageous construction, the outer lateral faces ofthe upper and lower gripper elements in respective pairs are coplanarand a respective cutter blade is mounted in sliding contact with theouter face of each upper gripper element. When the gripper elementsclose to loosely grip a transverse thread the cutter blades are advancedacross the outer faces of the pairs of gripper elements to sever thethread at both ends at the faces of the gripper elements.

The invention will be further described by way of example by referenceto one embodiment thereof, which is illustrated in the accompanyingdrawings.

in the drawings:

FIG. 1 is a side elevation of a net-making machine according to thisinvention;

FIG. 2 is a partial end elevation of the die assemblies and associatedstructure in the machine shown in FIG. 1; and

FIGS. 3 and 4 are partial cross-sections of the die assemblies andassociated structure shown in FIG. 2, showing two stages in the cycle ofoperation of the machine.

In the machine shown in the drawings a base carries a net-making unit 11and a take-off unit 12. The net-making unit includes a longitudinallyreciprocable carriage having upper and lower portions 13a and 13b whichare moved together as shown by the arrows in FIG. 1 by a lever mechanism14 actuated by a hydraulic system 15, which may be constructed inaccordance with conventional principles and for the sake of clarity isnot shown in detail. A transverse thread or weft drawing deviceindicated generally at 16 is also driven hydraulically.

The upper portion 130 of the carriage carries a transverse bar 17, bestseen in FIGS. 2 to 4, in which is formed a row of upper moulding diecavities 18. The cavities are in communication with the outlet nozzlesof individual moulding injectors 20 provided for each thread crossing.The injectors each include a heated barrel 2], a feed hopper 22 forgranular thermoplastic and hydraulicmechanism 23 for actuating a pistonin the barrel. They may be constructed in accordance with conventionalprinciples and are not concerned in the present invention. The bar 17also carries a guide plate 24 which extends downwardly in advance of themoulding dies and is formed with V-shaped guideways 25 to locate thelongitudinal or warp threads accurately in relation to the dies.

in accordance with the invention, alongside the two outermost dies atthe ends of the bar 17 are two respective upper gripper elements 26having plane outer faces, and beyond the gripper elements are respectivecutter blades 27 which are reciprocable vertically by hydraulicmechanism indicated generally at 28.

In accordance with the invention also, there are located in the bar 17between the die cavities l8 thread diverting elements 30. These elementslie on the line of centers ofthe die cavities and are retained in thebar 17 by screw threads 31 by which their vertical position is alsoadjustable. Polygonal heads 32 facilitate adjustment of the elements andlock nuts 33 ensure that the selected position is maintained. Theprojecting ends or noses of the elements 30 are formed with a number ofintersecting radial grooves 34 which serve to guide a transverse threadpassing across the noses of the elements. The provision of a number ofsuch grooves permits adjustment of the vertical position of the elementsto a fraction of the pitch of the mounting threads 31. Alternative formsof diverter element and alternative mountings may be used, bearing inmind that it is preferable that the element should provide a guidewayfor the weft thread and the mounting should permit vertical adjustment.

The lower portion 13b of the carriage bears a transverse row of lowermoulding die portions 40 with cavities 41 corresponding to the upper diecavities 18. The die portions are formed with grooves 42 to accommodatethe warp and weft threads which will pass through the dies. The lowerdie portions are carried on shafts 43 by means of which they can beraised by hydraulic mechanism (which can be of conventional type and isnot shown) to close the dies.

In accordance with this invention, two lower gripper elements 44 aredisposed at the ends of the row of lower die portions 40 and are carriedby shafts 45 by means of which they can be raised by hydraulic mechanism(not shown). The hydraulic drive for these elements is arranged to raisethe elements immediately before closure of the dies but only to aposition in relation to the upper gripper elements 26 where a weftthread passing between the elements will be lightly gripped.

The carriage is also provided with front grippers 46 (see FIG. 1) in theform of one upper and two cooperating lower members between which thewarp threads entering the machine can be gripped. Similar rear grippersare provided at 47 to grip the newly formed netting. A further pair offront and rear grippers are mounted on the fixed frame of the machinebut are not shown in FIG. 1 in order not to obscure the drawing withunnecessary detail.

The weft drawing device 16, which is hydraulically powered, includes atransversely extending endless chain 50 passing over end sprockets andcarrying weft thread grippers 51, one of which is shown in FIG. 2.

The jaws of the weft thread grippers are opened and closed by levers 52actuated by cam plates 53 in a manner already known in the textile artsand the grippers are carried by the upper reach of the chain 50 acrossthe machine along a line which will intersect the axes of the dieassemblies when the latter reach their closing position. I

The take off unit 12 is in the form of a chain conveyor 54 adapted tosupport the mesh structure of the netting produced by thenet-making unit11 and deliver it in a regular and controlled manner. The conveyor isdriven intermittently in time with the moulding cycle of the net-makingunit, for example by a rack mechanism located at 55.

In operation, warp threads L consisting of or containing thermoplasticfibers or filaments, for example of polyethylene, are drawn from a bankof cheeses or other supply, passed through the front grippers 46,between the die portions and through the rear grippers 47, and alsothrough the grippers (not shown) on the fixed part of the machine. Aweft thread T is drawn from a cheese or other supply of a similarthread, also including a thermoplastic, and preferably the samethermoplastic as the warp threads. The diverter elements 30 are eachadjusted to compensate for the shrinkage previously observed to occurwhen the threads are bonded together during injection moulding.

In a single cycle of operation, the weft draw chain 50 is movedintermittently to carry the gripper 51 shown in FIG. 2 across themachine in the direction of the arrow. The jaws of the gripper are atthis time closed and a fresh length of the weft thread T is drawn acrossthe machine in the position which the dies will take up for moulding. Atthis time the carriage is retracted and the upper and lower die portionsmove apart to release the previous bonded weft thread. As the gripper 51reaches the opposite side of the machine the next gripper comes intoposition to take up a further length of thread T for the next weftinsertion. At this time the carriage with the dies open is moved to itsfront position, that is, at the extreme left hand end of its travel asseen in FIG. 1, and the grippers 46 and 47 are closed, clamping the warpthreads L in relation to the carriage. The upper portion 13a of thecarriage carrying the upper die cavities 18 is then lowered, togetherwith the upper gripper elements 26 and the cutter blades 27.

The lower gripper elements 44 are then raised into engagement with thecorresponding upper elements and at the same time the cutter blades 27are lowered across the outer face of the gripper elements 26 and 44.FIG. 3 shows the position of the essential parts of the machine at thisstage, where the weft thread T is loosely gripped between the gripperelements 26 and 44 and the blade 27 has severed the inserted weft threadfrom the supply. The gripper elements 44 then remain stationary whilethe lower die portions 40 are raised to enclose the weft and warpthreads T and L in the die cavities 18,41. As the dies close the weftthread suffers minor deviation where it crosses the warps in thecavities but a more extensive deviation over the diverter elements 30and the ends of the thread T are drawn in between the gripper elements26 and 44 to permit such deviation, as shown in FIG. 4, substantiallywithout tension in the thread T.

The injectors then inject heated thermoplastic, which may be of the samechemical type as the thermoplastic material of the threads, into the diecavities to form moulded masses therein which bond the weft thread toeach warp thread. The carriage, with the warps still clamped to it,moves to its rear position, that is to the right as seen in FIG. 1 andcarries the warps with the bonded weft for a distance equal to the meshdimension of the netting. When the carriage has reached its rearposition, the front and rear grippers on the fixed part of the machineclose to clamp the warps and netting in the new position and the frontand rear grippers 46 and 47 on the carriage release the warps. The diesand the gripper elements 26 and 44 then reopen and the carriage is freeto return to its front position for the beginning of a fresh cycle.

I claim:

1. Apparatus for producing netting comprising:

means for advancing a plurality of longitudinal threads; means fordrawlng at least one transverse thread across the longitudinal threads;

a transverse row of openable die assemblies each adapted to receive andenclose portions of one longitudinal and one transverse thread at athread crossing;

means for introducing a heated plastics material into the die assembliesto form a moulded mass therein;

and thread diverting means disposed between adjacent die assemblies toextend the path of a transverse thread between said die assemblies tocounteract the contraction of the transverse thread which occurs on theintroduction of the heated plastics material.

2. Apparatus according to claim 1 in which said diverting means comprisethread diverting elements located between each individual die assembly.7

3. Apparatus according to claim 2 in which the thread diverting elementsare adjustable.

4. Apparatus according to claim 2 in which each thread diverting elementis provided witha guideway to receive and guide a transverse thread.

5. Apparatus according to claim 3 in which the thread diverting elementsare mounted on screw threads.

6. Apparatus according to claim 1 in which at least some of the dieassemblies are selectively operable whereby the apparatus can be used toproduce netting with different numbers of longitudinal threads.

7. Apparatus according to claim 1 in which more than one transverselyextending row of die assemblies is provided, whereby more than onetransverse thread can be bonded to the longitudinal threads in a singlecycle of operation.

8. Apparatus according to claim 1 including gripper elements at oppositeends of the row of die assemblies and adapted to loosely grip theopposite ends of a transverse thread whereby diversion of the thread isaccomplished substantially without tension in the transverse thread.

9. Apparatus according to claim 8 including cutters disposed against theouter lateral faces of the gripper elements and movable to sever thetransverse thread prior to closure of the die assemblies.

1. Apparatus for producing netting comprising: means for advancing aplurality of longitudinal threads; means for drawing at least onetransverse thread across the longitudinal threads; a transverse row ofopenable die assemblies each adapted to receive and enclose portions ofone longitudinal and one transverse thread at a thread crossing; meansfor introducing a heated plastics material into the die assemblies toform a moulded mass therein; and thread diverting means disposed betweenadjacent die assemblies to extend the path of a transverse threadbetween said die assemblies to counteract the contraction of thetransverse thread which occurs on the introduction of the heatedplastics material.
 1. Apparatus for producing netting comprising: meansfor advancing a plurality of longitudinal threads; means for drawing atleast one transverse thread across the longitudinal threads; atransverse row of openable die assemblies each adapted to receive andenclose portions of one longitudinal and one transverse thread at athread crossing; means for introducing a heated plastics material intothe die assemblies to form a moulded mass therein; and thread divertingmeans disposed between adjacent die assemblies to extend the path of atransverse thread between said die assemblies to counteract thecontraction of the transverse thread which occurs on the introduction ofthe heated plastics material.
 2. Apparatus according to claim 1 in whichsaid diverting means comprise thread diverting elements located betweeneach individual die assembly.
 3. Apparatus according to claim 2 in whichthe thread diverting elements are adjustable.
 4. Apparatus according toclaim 2 in which each thread diverting element is provided with aguideway to receive and guide a transverse thread.
 5. Apparatusaccording to claim 3 in which the thread diverting elements are mountedon screw threads.
 6. Apparatus according to claim 1 in which at leastsome of the die assemblies are selectively operable whereby theapparatus can be used to produce netting with different numbers oflongitudinal threads.
 7. Apparatus according to claim 1 in which morethan one transversely extending row of die assemblies is provided,whereby more than one transverse thread can be bonded to thelongitudinal threads in a single cycle of operation.
 8. Apparatusaccording to claim 1 including gripper elements at opposite ends of therow of die assemblies and adapted to loosely grip the opposite ends of atransverse thread whereby diversion of the thread is accomplishedsubstantially without tension in the transVerse thread.